The invention relates to a sensor arrangement for a centrifugal pump unit.
Rotary speed controlled centrifugal pump units are considered these days as the state of the art. In particular with circulatory pumps employed in heating installations, the rotary speed control serves for adapting the pump power as optimally as possible to the respective operation condition of the installation, on the one hand to be able to operate the installation as advantageously as possible with respect to energy, and on the other hand to avoid flow noise in the installation. Whilst with pump units with radial wheels, in particular of a small construction and a comparitively low rotary speed, the control variable (rotary speed of the pump) may be effected in a simple manner by acquisition of the electrical variables of the driving motor, with centrifugal pump units of a greater power, higher rotary speed and in particular with pump units with a semi-axial impeller it is demanded that hydraulic variables of the pump are acquired, since in this region the electrical variables of the driving motor behave almost independently of the rotary speed. Such an acquisition of hydraulic variables is clearly more complicated and is today as a rule carried out with the help of an external differential pressure gauge, which via lead connections is connected between the pressure connection piece and the suction connection piece of the pump. Such an arrangement is known for example from DE 39 23 027 A1.
The mounting of such an external differential pressure gauge is complicated, since apart from the electronic apparatus to be separately supplied, a tubing must be effected thereto. This tubing is not only complicated with respect to assembly, but is also sensitive, since these relatively thin tubes may easily be damaged by mechanical external influences.
Furthermore modern frequency converter controlled centrifugal pumps are not only rotary speed controlled but are also variable in their control characteristic. In order to adapt the control characteristic in a suitable manner to the respective operating condition of the installation, it has been shown to be useful to acquire the temperature of the medium to be delivered. This may be effected by a separate sensor for example arranged in the pump housing, which however brings with it corresponding changes on the pump housing side and furthermore necessitates also a separate wiring.